Investigations in the coming year will include work in four areas: (1) Characterization of GH releasing activity in rat hypophyseal portal blood. (2) Generation of an antibody to dopamine, and use of this antibody to investigate the role of dopamine in inhibiting prolactin release from the pituitary. (3) Investigating factors governing the release of somatostatin from the pancreas and gut, in vivo, and in vitro analysis of factors influencing the release of somatostatin from pancreatic islets. (4) We have demonstrated that small doses of D-Trp6-LHRH increased and large doses decreased testicular LH receptors by direct action. We will examine if similar findings are obtained for FSH and prolactin receptors.